Apparatus and method for batch non-contact material characterization

ABSTRACT

An apparatus for performing non-contact material characterization includes a wafer carrier adapted to hold a plurality of substrates and a material characterization device, such as a device for performing photoluminescence spectroscopy. The apparatus is adapted to perform non-contact material characterization on at least a portion of the wafer carrier, including the substrates disposed thereon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Patent Application No. 61/066,074 filed Feb. 15, 2008, thedisclosure of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

Various non-contact material characterization techniques are known andare commonly used to measure semiconductor wafers. Non-contact materialcharacterization techniques include: X-ray diffraction (“XRD”), eddycurrent measurements, and photoluminescence spectroscopy, among others.Photoluminescence spectroscopy, for example, is a technique whereinlight is directed from a pump beam onto a sample, such as asemiconductor wafer. Such light may first be absorbed by the materialand then dissipated, such as through emission of light (also known as“luminescence”). By measuring the intensity and spectral content of theluminescence by means of collection optics, various important materialproperties may be gleaned. Such properties revealed by photoluminescenceinclude: determination of band gap, material quality (including theconcentration of impurities and defects), composition of the differentsemiconductor layers, among many other properties. One useful way ofanalyzing the data may include plotting photoluminescence intensity as afunction of wavelength. The full width at half maximum (“FWHM”) may thenbe measured and plotted.

Currently, such material characterization techniques are performedoutside of the epitaxial growth apparatus in which the semiconductorwafers are formed. Commonly, the wafers are removed from the epitaxialgrowth apparatus and placed into cassettes of wafers. The cassettes arethen cycled through, and the non-contact material characterizationtechniques are conducted on a wafer-by-wafer basis, with one wafer beingtested at a time. This process can take a considerable amount of time.

Further adding to current processing times is the fact that typicalprocessing apparatuses utilize a chamber referred to as a “load lock” inaddition to the principal process chamber. A substrate, or a wafercarrier holding numerous substrates, is inserted into the load lock andbrought to equilibrium with an inert atmosphere in the load lockcompatible with the epitaxial growth process. Once the substrates are atequilibrium with the inert atmosphere in the load lock, a door betweenthe load lock and the process chamber itself is opened, and thesubstrates are advanced into the process chamber. After processing, thesubstrates are removed from the process chamber through the load lock.Multiple handling into and out of the epitaxial growth apparatus takesconsiderable time, which in turn, slows the process.

With regard to photoluminescence techniques, for example, the wafers aretypically placed on a stage and the pump beam and collection optics areeither moved in a raster-scan or an outwardly spiraling pattern. Thatis, in the case of a raster-scan, the pump beam and collection opticsare moved linearly across the surface in a first direction from one endof the wafer to the other. After fully scanning a first line across thewafer, the pump beam and collection optics are moved a small,incremental distance perpendicular to the first direction, and then theyproceed to linearly scan across the surface parallel to and adjacent tothe first line. This process is repeated until the entire surface of thewafer has been scanned. This technique is analogous to, for example,reading lines of text across the surface of a page from left to rightand incrementally moving from the top line to the bottom. In the case ofan outwardly spiraling pattern, however, the pump beam and collectionoptics begin scanning at the center of the wafer, and then they proceedto spiral outwardly from the center until the entire surface of thewafer has been scanned.

The above described prior art method of performing non-contact materialcharacterization techniques can be very inefficient. Particularly in thecase where multiple processes are to be performed on a group ofsemiconductor wafers, with material characterization occurring betweeneach process, it can take a substantial amount of time to complete theoverall process. Specifically, it can be very time consuming to firstremove all of the wafers from the epitaxial growth apparatus after oneprocess is completed, then to perform the testing on each wafer one at atime, and then to reseat the wafers on a wafer carrier and introduce thewafers to the same or a different apparatus for further processing.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention provides an apparatus for performingnon-contact material characterization on substrates. The apparatus inaccordance with this aspect of the invention desirably includes a wafercarrier and a non-contact material characterization device. The wafercarrier desirably has a top surface constructed and arranged to hold atleast one substrate thereon. The non-contact material characterizationdevice is desirably constructed and arranged to perform a non-contactmaterial characterization technique on at least a portion of at leastone substrate held on the wafer carrier.

The apparatus may further include an epitaxial growth apparatus having aload lock. The non-contact material characterization device is desirablyconstructed and arranged to perform the non-contact materialcharacterization technique while the wafer carrier is disposed withinthe load lock of the epitaxial growth apparatus.

A computational device may be connected to the non-contact materialcharacterization device and connected to an epitaxial growth apparatus.The computational device is preferably constructed and arranged toprocess data from the non-contact material characterization device.Further, the computational device may be operative to adjust conditionsin the epitaxial growth apparatus based on the data processed by thecomputational device.

The non-contact material characterization device may comprise a devicefor performing photoluminescence spectroscopy.

Still other aspects of the present invention provide methods forperforming non-contact material characterization on substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an apparatus in accordance with oneembodiment of the invention.

FIG. 2 is a schematic diagram of an epitaxial growth apparatus and loadlock in conjunction with an apparatus in accordance with one embodimentof the invention.

FIG. 3 is a schematic diagram of a transfer chamber in accordance withone embodiment of the invention.

DETAILED DESCRIPTION

In describing the preferred embodiments of the invention illustrated inthe appended drawings, in which like reference numerals represent likeelements, specific terminology will be used for the sake of clarity.However, the invention is not intended to be limited to the specificterms so selected, and it is to be understood that each specific termincludes all technical equivalents that operate in a similar manner toaccomplish a similar purpose.

An apparatus in accordance with one embodiment of the invention isillustrated in FIG. 1. A wafer carrier 10 is shown holding a pluralityof substrates, such as wafers 12. The wafers 12 are preferably held bystructures such as pockets (not shown). The wafer carrier 10 ispreferably generally circular in shape, although this is not required,and the carrier 10 is preferably composed of a material such asgraphite.

The wafer carrier 10 is shown mounted on a spindle 14, which may rotateabout axis 15 under the influence of a rotation control device, such asmotor 16. The motor 16 is preferably connected to a control device 18,which will be discussed in detail below. The motor 16 is preferablyadapted to precisely control the angular position and rotationalvelocity of the wafer carrier 10. Useful motors 16 for this applicationmay include stepper motors and servos, for example.

The connection (not shown) between the spindle 14 and the wafer carrier10 is designed so that the wafer carrier 10 may releasably mate with thespindle 14. The connection is preferably configured so that the wafercarrier 10 may be secured to the spindle 14 in such a way that the wafercarrier 10 and spindle 14 may rotate in a fixed angular relationship.The connection is also preferably configured to allow the wafer carrier10 to be easily detached from the spindle 14, so that the wafer carrier10 can be moved.

As schematically shown in FIG. 2, the wafer carrier 10 is shown in theload lock 102 of an epitaxial growth chamber 100. The load lock 102 isequipped with a chamber door 104 and an exterior door 106. When thechamber door 104 is opened, the interior space within load lock 102communicates with the interior space of the epitaxial growth chamber100. When door 104 is closed, the load lock 102 is isolated from theepitaxial growth chamber 100. When door 106 is open, the load lock 102is open to the exterior of the apparatus, and most typically, is open toroom air. The interior space within load lock 102 is connected to asource of a substantially inert gas, so that the interior space withinthe load lock 102 may be maintained under an atmosphere of thesubstantially inert gas. As used in this disclosure, the term“substantially inert gas” refers to a gas which does not causesubstantial, detrimental reactions with the substrates or layersdisposed on the substrates under the conditions prevailing in the loadlock. Merely by way of example, for typical substrates carrying layersof III-V semiconductors, gases such as nitrogen, hydrogen, group VIIInoble gases, and the like, and mixtures of these gases can be employed.

A conveyor (not shown) may be provided within the load lock 102, theconveyor being configured to move the wafer carrier 10 into or out ofthe epitaxial growth chamber 100 while the chamber door 104 is open. Theconveyor may include any type of mechanical element capable ofmanipulating the wafer carrier 10, such as, for example, robotic arms,linear slides, pick-and-place mechanisms, mobile chains or belts, orcombinations of these elements.

During a preferred use of the apparatus of the present invention, thefollowing steps are carried out in order to perform a non-contactmaterial characterization technique on the wafers 12. After one cycle ofepitaxial growth processing is completed on the wafers 12, the door 104is opened and the wafer carrier 10 is detached from spindle 116. Thecarrier 10 is then moved from the epitaxial growth chamber 100 into theload lock 102 by the conveyor. The carrier 10 is then mated to thespindle 16. While the wafer carrier 10 is thus disposed within the loadlock 102, at least one non-contact material characterization techniqueis performed, as described in detail below.

It is to be noted that by performing non-contact materialcharacterization measurements while the wafer carrier 10 is in the loadlock 102, overall processing time for the substrates will preferably bereduced. Specifically, the amount of time required to move the carrier10 into and out of the load lock 102 through door 106 in order toperform tests on the substrates is eliminated. Also eliminated is theadditional time required allow the atmosphere in the load lock 102 toreach equilibrium, since the wafer carrier 10 is not required to beremoved from the load lock 102 during testing and the exterior door 106is not required to be opened.

A further benefit of performing the material characterization techniquein the load lock 102 is the fact that information gathered from thetesting can be used to control one or more of the processes. Forexample, the information gathered can be processed by a programmedcomputational device integrated with the epitaxial growth apparatus. Thecomputational device may be connected to or incorporated with thecontrol device 18. The computational device is preferably integratedwith the epitaxial growth apparatus in such a way that, based on theinformation gathered by the computational device, the conditions in thegrowth chamber 100 may be adjusted to optimize the conditions for asubsequent set of substrates. Alternatively or additionally, thecomputational device may use the information obtained by the non-contactmeasurement to adjust the process to be applied to the substrates onthis particular carrier 10 in a subsequent step, as for example, duringfurther treatment in process chamber 100 or in a different processchamber.

In a typical epitaxial growth apparatus, the wafers 12 are first removedfrom the epitaxial growth apparatus, and then they are tested in aremote lab, after which the data from the testing may be used tooptimize the conditions in the growth chamber. The time it takes toperform those steps creates significant “loop delay,” as severalprocesses may have been performed in the growth chamber under theprevious process conditions before the conditions are modified based onthe material characterization tests. In contrast, by performing thematerial characterization techniques in the load lock 102 and, thus,quickly providing information to control subsequent processes, theapparatus of the present invention reduces any such “loop delay.”

The mechanisms for conducting non-contact material characterization inaccordance with a preferred embodiment of the invention will now bediscussed. Referring again to FIG. 1, shown mounted above the wafercarrier 10 is a non-contact material characterization device, such as,for example, a photoluminescence device 20. The photoluminescence device20 may include a pump beam emitter 22 and collection optics 24. The pumpbeam emitter 22 may be configured to project a precisely defined beam oflight at the top surface 40 of the wafer carrier 10, so that the lightmay either reflect back to the collection optics 24 or so that theluminescence of the material at the top surface 40 of the carrier 10 maybe measured by the collection optics 24.

The photoluminescence device 20 is preferably configured to preciselycontrol the frequency of the emitted beam of light. Precise control overthe various parameters of the photoluminescence system, such asfrequency of the emitted light, will preferably make the entire systemmore accurate. Furthermore, frequency of the light emitted from the pumpbeam emitter 22 may be varied in order to target different layers of thesemiconductor for analysis. That is, because different layers in asemiconductor having different band gaps will absorb differentfrequencies of light, the different layers of the semiconductor may betargeted for analysis by selecting the appropriate frequency of light tobe absorbed by that layer.

The photoluminescence device 20 as described above is per se aconventional device.

The device 20, in accordance with a preferred embodiment of the presentinvention, is preferably mounted to a translation mechanism 30 whichoperates to translate the photoluminescence device 20 along a guidingapparatus, such as a guiding rail 32. The translation mechanism 30 maycomprise any known mechanism for translating a device in at least onedimension. Appropriate translation mechanisms 30 may include, forexample, linear actuators, belt drives, screw drives, etc.

The translation mechanism 30 and guiding rail 32 are preferably arrangedso that the photoluminescence device 20 may scan at least a portion ofthe wafer carrier 10. In the embodiment illustrated in FIG. 1, thetranslation mechanism 30 and guiding rail 32 are arranged so that thephotoluminescence device 20 may translate back and forth in onedimension across the top surface 40 of the wafer carrier 10.Specifically, in the illustrated embodiment, the photoluminescencedevice 20 preferably scans the top surface 40 radially with respect toaxis 15, moving between the center 42 and the outer edge 44 of the wafercarrier 10. In this way, the device 20 may scan the entire top surface40 of the wafer carrier 10. That is, the photoluminescence device 20 mayscan a line across the top surface 40 from, for example, the center 42of the wafer carrier 10 in a radial direction to the edge 44. Once thedevice 20 reaches the edge 44, the motor 16 preferably rotates the wafercarrier 10 about axis 15 by a small degree increment. The device 20 thenscans again, for example, from the edge 44 to the center 42. Thisprocess is repeated, with the position of the wafer carrier 10 beingincrementally rotated with each pass of the photoluminescence device 20until a complete revolution of the wafer carrier 10 has been made.

During the above-described movement of the photoluminescence device,while the pump beam emitter 22 projects light at the top surface 40 ofthe wafer carrier 10, the collection optics 24 measure the luminescenceof the target portion of the material. The information received by thecollection optics 24 may include data such as intensity and wavelengthof the collected light. This data is collected as a series of samplesrepresenting the measured values of each variable corresponding to eachdiscrete sampled location on the top surface 40 of the wafer carrier 10.By taking samples at many discrete locations (which are very close toeach other), the entire top surface 40 of the wafer carrier 10,including the top surfaces of the wafers 12, may be accurately mapped.

The data collected from the photoluminescence device 20 is preferablystored in a memory device 46, which may be a component of the controldevice 18. The data is preferably associated with the geometricalposition of each sampled point P. The position of each point P may bedescribed in many ways, such as Cartesian coordinates. In oneembodiment, however, the location of each sample point P may bedescribed by that point's radial coordinates about axis 15. In order todefine radial coordinates, the wafer carrier 10 preferably has areference axis 50 extending from the center 42 of the wafer carrier 10.Thus, each point P may be defined by its radial distance R from thecenter 42 of the wafer carrier 10 and by its angle θ from the referenceaxis 50.

After completing a scan of the wafer carrier 10, the memory device 46will preferably have all of the photoluminescence data regarding the topsurface 40. The memory device 46 also preferably contains informationregarding the geometry of the wafer carrier 10, including therelationships of the pockets (which hold the wafers 12) to referenceaxis 50 and the radial distances of such pockets from center 42. Fromthis data, information regarding each semiconductor wafer 12 may becalculated. That is, by coordinating the input data with itscorresponding radial coordinates, and by comparing the coordinates tostored information regarding the geometry of the wafer carrier 10, thecontrol device 18 may correctly link the data from eachphotoluminescence measurement with the appropriate wafer 12 and with aparticular location on the wafer 12.

In this embodiment of the apparatus of the present invention, a controldevice 18 is designed to fully operate all components of the apparatus.That is, the control device 18 may be adapted to control the movement ofthe motor 16. The control device 18 is also preferably configured tocontrol the movement of the photoluminescence device 20, by providingappropriate signals to the translation mechanism 30. Further, thecontrol device 18 preferably controls the photoluminescence device 20itself, including the pump beam emitter 22, and the intensity andfrequency of the light emitted therefrom. The control device 18 alsopreferably receives and processes the input from the collection optics24, as described above. The control device 18 may include a programmedgeneral purpose computer or a portion of such a computer, or may includeplural computational elements physically separate from one another butconnected to one another.

The apparatus as described above will preferably speed up the overallprocessing time for substrates, such as semiconductor wafers 12. Inaddition to eliminating the time required to remove the wafers 12 fromthe load lock 102 for testing, as described above, the apparatus of thepresent invention may further increase efficiency by processing multiplewafers 12 in batches. That is, the apparatus is preferably constructedto scan the entire top surface 40 of a wafer carrier 10 holding manywafers 12, rather than scanning each wafer 12 one at a time.

Many alternatives to the preferred embodiment are encompassed by thepresent invention, not all of which are described herein. For example,though the above-described reference axis 50 is preferably one definedby the motor 16, in an alternative embodiment there may be a rotaryencoder (not shown) connected to the spindle 14, which provides data tothe control device 18 regarding the angle θ. Alternatively, a physicalaxis or mark 52 on the top surface 40 of the wafer carrier 10 may definethe axis 50. Such mark 52 is preferably observable by thephotoluminescence device 20, such as by constructing it of a materialhaving known photoluminescent properties. In that way, the controldevice 18 may be able to deduce the radial orientation of the wafercarrier 10 after completing the full scan of the surface 40 and aligningthe data with the observed reference axis 50. In a further alternative,no physical mark 52 need be present, and the geometry of the top surface40 of the wafer carrier 10 may be rotationally asymmetric, such as, forexample, by having at least one gap between the wafer pockets be largerthan the others. In this embodiment, the data from the complete scan ofthe top surface 40 may be compared to known information about thegeometry of the wafer carrier 10, and the control device 18 mayaccordingly deduce the rotational coordinates of each sample point P andassign the correct data to the appropriate wafers 12. By constructingthe wafer carrier 10 of material having no photoluminescent properties,the control device 18 will be able to distinguish between the wafers 12and the carrier 10, and the device 28 will be able to assign the correctdata to the appropriate wafers 12 accordingly.

Further, the present invention is not limited to the above-describedmanner of scanning the surface 40 of the wafer carrier 10. Alternativemethods may be employed consistent with the present invention. Forexample, the photoluminescence device 20 may scan the surface 40 byscanning in concentric circles. For instance, the beam from thephotoluminescence device 20 may start at the center 42 of the wafercarrier 10 and step out one increment in a radial direction. The device20 may then scan while the motor 16 fully rotates the wafer carrier 10once about axis 15. The device 20 may then step out again and thecarrier 10 may be rotated once again. This process may be continueduntil the entire top surface has been scanned. In a similar alternative,the device 20 may perform an outwardly spiraling scan by graduallymoving radially outwardly from the center 42 while the wafer carrier 10continuously rotates.

In a further alternative embodiment, the translation mechanism 30 andguiding rail 32 may be arranged so that the photoluminescence device 20may translate in two dimensions across the top surface 40 of the wafercarrier 10. For instance, the guiding rail 32 may be mounted on anotherdevice, such as a second guiding rail (not shown), which is configuredto translate along an axis perpendicular to the guiding rail 32. Inaccordance with such an embodiment of the invention, the wafer carrier10 may be scanned by, for example, moving the photoluminescence device20 in a raster-scan, an outwardly spiraling pattern, or a concentriccircle pattern, as described above, over the entire top surface 40 ofthe carrier 10.

In a further alternative embodiment, the translation mechanism 30 may bereplaced by a different means for moving a beam of radiant energy acrossthe surface of the wafer carrier, such as a pivoting mechanism, whichmay move the beam of light around by pivoting in one or two dimensions.

It is to be further noted that the present invention is not limited tolocating the non-contact material characterization device, such as thephotoluminescence device 20, in a position directly above the wafercarrier 10. Alternative arrangements of the device 20 may be used. Forexample, a mirror or other optical device may be attached to thetranslating mechanism 30 instead of the photoluminescence device 20. Insuch an embodiment, the photoluminescence device 20 may be disposed in alocation remote from the optical device, where it may be configured toproject the beam of light towards and receive the reflected light backfrom the optical device. The optical device may then redirect such beamsof light towards the top surface 40 of the wafer carrier 10. Then, bytranslating the optical device in the manner described above withrespect to the photoluminescence device 20, the top surface 40 of thewafer carrier 10 may be similarly scanned without requiring thephotoluminescence device 20 itself to be translated. Such optical devicemay similarly pivot instead of translating, as described above.

In a further alternative, an apparatus in accordance with the presentinvention need not be incorporated with load lock 102. Instead, theapparatus may be located in and incorporated with a transfer chamber,such as that shown and described in U.S. Provisional Application No.61/066,031 filed Feb. 15, 2008, and entitled “Cluster Tool and Processfor III-V Materials” [hereinafter “the Cluster Tool application”], theentire disclosure of which is fully incorporated by reference herein.The transfer chamber of the Cluster Tool application is a chamber incommunication with a plurality of adjacent process chambers. Asdescribed in such application, such a configuration may be beneficiallyused where multiple different processes, each having different processchambers, are to be performed on a substrate. In order to speed up theoverall process time on such substrate, the transfer chamber may beadapted to provide an inert atmosphere through which the substrate maybe transferred from one process chamber to another. In accordance withthe present invention, it may further speed up the overall process timeon the substrate to incorporate the apparatus of the present inventioninto such transfer chamber, where it may be configured to performnon-contact material characterization on the wafer carrier 10 while itis located in the transfer chamber.

An example of such a transfer chamber is shown in FIG. 3, whichillustrates a plurality of processing chambers 210, 212, 214, 216, 218,and 220, and a transfer chamber 222. The processing chambers 210-220 arephysically connected to the transfer chamber 222 so that the interiorspace within each processing chamber can communicate with the transferchamber. Each processing chamber 210-220 is equipped with a door 224arranged to selectively permit or block such communication. For example,in the condition depicted in FIG. 3, the doors 224 associated withchambers 210, 212, 214, and 216 are in their respective closedpositions, whereas the doors 224 associated with chambers 218 and 220are in their open positions so that the interior spaces within chambers218 and 220 are in communication with the interior of transfer chamber222. Each processing chamber is arranged to receive a carrier 226holding a plurality of growth substrates 228 such as flat wafers of acrystalline material, and to perform a process on the substrates whilethe substrates are disposed within the processing chamber. Theindividual processing chambers are arranged to perform differentprocesses. For example, chamber 210 is arranged to perform a hydridevapor phase epitaxial growth process (referred to herein as “HVPE”),process chambers 212 and 214 are arranged for MOCVD, and additionalreaction chambers 216, 218, and 220 are equipped to perform otherprocesses. Merely by way of example, these other processes may includedeposition of metals to serve as conductors; epitaxial growth byprocesses such as molecular beam epitaxy, atomic layer epitaxy, or thelike; etching of the substrates or of layers deposited on thesubstrates; or any other process which can be applied to a substrate,with or without compound semiconductor thereon. Each such chamberdesirably is optimized for the particular process or processes to beperformed therein.

The apparatus also includes load locks 248 and 250. Load lock 248 isequipped with a transfer chamber door 252 and an exterior door 254. Loadlock 250 is equipped with a similar transfer chamber door 256 andexterior door 258. The interior space within transfer chamber 222 isconnected to a source 260 of a substantially inert gas, so that theinterior space within the transfer chamber 222 may be maintained underan atmosphere of the substantially inert gas. The substantially inertgas may be the same as, or different from, the carrier gases employed inone or more of the reaction chambers, and hence source 260 may becombined with one or more of the other carrier gas sources. Load locks248 and 250 desirably are also connected a source of a substantiallyinert gas, which may be the same source 260 or a different source.

A conveyor 262 is also provided within transfer chamber 222. Theconveyor is schematically depicted in FIG. 1 as an arm capable of movingin circumferential directions around a central axis 264 and radialdirections towards and away from the axis. In other embodiments, theconveyor may include any type of mechanical element capable ofmanipulating carriers 226, as for example, elements such as linearslides, pick-and-place mechanisms, mobile chains or belts, orcombinations of these elements. Also, the circular shape of transferchamber 222 depicted in FIG. 3 is merely illustrative. Conveyor 262 isarranged so that it can move wafer carriers into or out of any of theprocess chambers 210-220 while the associated doors 224 of thesechambers are open. The conveyor also can move wafer carriers into or outof load locks 248 and 250 when doors 252 and 256 are open. The conveyoris arranged so that it can transfer carriers 226 between the variouschambers, as for example, out of either of the load locks into any ofthe process chambers, or out of any of the process chambers into anyother process chamber or into any of the load locks. Conveyor 262 may bearranged to move every wafer in the same sequence, so that every wafercarrier will be moved through the same set of process chambers in thesame order. More preferably, however, conveyor 262 is controlled by aprogrammable or selectively operable mechanism, as for example, one ormore electrical, mechanical, or hydraulic components linked to one ormore programmable controllers, so that the sequence of movements betweenchambers can be varied, either for different process runs or forindividual wafers within a process run.

The transfer chamber also may be provided with one or more non-contactmaterial characterization devices 266, arranged to direct one or morebeams of radiant energy to or through substrates 228 held on a carrier226 while the carrier is disposed within the transfer chamber, and tomonitor one or more properties of the substrates or materials depositedon the substrates based on interactions between the radiant energy andthe substrate. The transfer chamber may be equipped with a standschematically depicted at 268 in FIG. 3 for holding a wafer carrier 226with substrates 228 thereon, and apparatus for moving the beam from thenon-contact material characterization device 266, the substrates, orboth, so that the substrates move relative to the beam, and the beampasses over different areas of the various substrates held on a carrier226. The movement apparatus may include, for example, a support linkedto a mechanical motion apparatus which can rotate the support 268, andhence, the wafer carrier about the axis of the wafer carrier. Themovement apparatus may be arranged to translate the wafer carrier indirections transverse to its axis. The movement apparatus also mayinclude apparatus for moving one or more components of the non-contactmaterial characterization device, so as to move the beam of radiantenergy. Merely by way of example, the non-contact materialcharacterization device may include a beam-directing element 270 such asa mirror, lens, holographic element, or the like, and the movementapparatus may be arranged to move the beam-directing element 270, so asto move the beam. Where the non-contact material characterization deviceis arranged to receive radiation from the substrate, as for example, ina photoluminescence measurement, the movement device similarly moves thefield of view of the non-contact material characterization device. Oneor both of the load locks 248, 259 may be equipped with a similarnon-contact material characterization apparatus 272.

In a method according to one embodiment of the invention, as thesubstrates are moved between the chambers, properties of the substrates,or the layers being grown thereon, can be monitored using thenon-contact material characterization device 266. The informationgathered in this manner can be used to control one or more of theprocesses. For example, a substrate removed from HVPE process chamber 10can be conveyed to the stand 268 and monitored using the non-contactmaterial characterization device 266. The information gathered in thisprocess can be used to optimize conditions in the HVPE process chamber210 for a subsequent set of substrates. Alternatively or additionally,the information obtained by the non-contact material characterizationcan be used to adjust the process to be applied to the substrates onthis particular carrier in a subsequent step, as for example, duringtreatment in MOCVD process chamber 212.

It is appreciated that various means for moving the beam of radiantenergy from the photoluminescence device 20 across the surface 40 of thewafer carrier 10 have been disclosed herein. Such means include the oneor two dimensional translation mechanism 30, discussed above, or thealternative pivoting mechanism. Other such means include the movementapparatus described in connection with the transfer chamber 222.

It is to be further noted that, though the above described embodimentsof the present invention have been described in combination with aspecific non-contact material characterization technique, namelyphotoluminescence spectroscopy, the present invention is not limited tothe use of such technique. Any other non-contact materialcharacterization technique may be used in conjunction with the apparatusof the present invention. For example, non-contact surface curvaturemeasurements may be made by directing a beam of light onto a surface ofa wafer 12 and detecting the position of the reflected beam. Such asurface curvature measurement technique is shown and described in, forexample, pending U.S. application Ser. No. 11/127,834 (“the '834application”), filed May 12, 2005, Pub. No. 2005/0286058, and entitled“Method and Apparatus for Measuring the Curvature of ReflectiveSurfaces,” the entire disclosure of which is fully incorporated byreference herein.

The apparatus of the present invention is also not limited to performingnon-contact material characterization techniques after a cycle ofepitaxial growth processing is completed. The apparatus may also performa pre-run check of the wafers 12 while the wafer carrier 10 is in theload lock 102, or the transfer chamber, and before the wafer carrier 10is moved into an epitaxial growth chamber 100 for processing. Forexample, a non-contact material characterization device in accordancewith the present invention may include a deflectometer, which mayoperate similarly to the non-contact surface curvature measurementapparatus described in the '834 application. Specifically, suchdeflectometer may direct a beam of light onto a surface of a wafer 12and detect the position of the reflected beam. If the position of thereflected beam deviates from its expected position, it may indicate thatthe wafer 12 is not sitting properly on the carrier 10. This may occur,for example, when a particle is underneath the wafer 12 when it isloaded on the wafer carrier 10, and the wafer 12 is not sitting parallelto the carrier 10 as a result. It would be beneficial to obtain thisinformation before processing is conducted on the wafers 12, becausenon-parallel seating will likely cause non-uniform thermal transfer tothe wafers 12 during processing.

Furthermore, it is contemplated that material characterizationtechniques involving physical contact with the wafers 12 may also beperformed consistent with the present invention. For example, theabove-described photoluminescence device 20 may be replaced with adevice having a probe that is configured to extend to the surface 40 ofthe wafer carrier 10, where it tests the material in contact therewith.Such device may be mounted to a translation mechanism 30, as describedabove, which may similarly move the probe so that it may scan the entiresurface 40 of the wafer carrier 10.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. An apparatus for performing non-contact material characterization onsubstrates, comprising: (a) an epitaxial growth apparatus having aprocessing chamber for depositing a material on at least one substrateheld on a wafer carrier, said epitaxial growth apparatus having anancillary chamber in communication with said processing chamber andconfigured to receive said wafer carrier; and (b) a photoluminescencedevice constructed and arranged to perform photoluminescencespectroscopy on the material deposited on the at least one substrateheld on said wafer carrier while said wafer carrier is disposed in saidancillary chamber.
 2. Apparatus as claimed in claim 1 wherein saidancillary chamber is a load lock.
 3. Apparatus as claimed in claim 1wherein said ancillary chamber is a transfer chamber in communicationwith a plurality of processing chambers.
 4. Apparatus as claimed inclaim 1 further comprising a computational device connected to saidphotoluminescence device and connected to said epitaxial growthapparatus, the computational device being constructed and arranged toprocess data from said photoluminescence device.
 5. Apparatus as claimedin claim 4 wherein the computational device is operative to adjustconditions in said epitaxial growth apparatus based on the dataprocessed by the computational device in order to optimize theconditions for a subsequent set of substrates.
 6. Apparatus as claimedin claim 1 wherein said wafer carrier is constructed of a materialhaving substantially no photoluminescent properties.
 7. Apparatus asclaimed in claim 1 wherein said photoluminescence device is constructedand arranged to direct at least one beam of radiant energy towards saidwafer carrier, and further comprising a means for moving the beam ofradiant energy across a surface of said wafer carrier.
 8. Apparatus asclaimed in claim 1 wherein said photoluminescence device is constructedand arranged to direct at least one beam of radiant energy towards saidwafer carrier, and further comprising a translation mechanism for movingthe beam of radiant energy across a surface of said wafer carrier. 9.Apparatus as claimed in claim 8 wherein the translation mechanism isconstructed and arranged to move the beam in one dimension. 10.Apparatus as claimed in claim 8 wherein said wafer carrier has a centerand an outer edge, the translation mechanism being constructed andarranged to move the beam between the center and the outer edge. 11.Apparatus as claimed in claim 8 wherein the translation mechanism isconstructed and arranged to move the beam in two dimensions. 12.Apparatus as claimed in claim 8 wherein said photoluminescence device isconstructed and arranged to perform a raster-scan across the surface ofsaid wafer carrier.
 13. Apparatus as claimed in claim 8 wherein saidphotoluminescence device is constructed and arranged to perform anoutwardly spiraling scan across the surface of said wafer carrier. 14.Apparatus as claimed in claim 8 wherein said photoluminescence device isconstructed and arranged to perform a concentric circle scan across thesurface of said wafer carrier.
 15. Apparatus as claimed in claim 1further comprising a rotation control device connectable to said wafercarrier, the rotation control device being constructed and arranged torotate said wafer carrier while said wafer carrier is disposed in saidancillary chamber.
 16. Apparatus as claimed in claim 1 wherein saidphotoluminescence device is disposed above said wafer carrier.
 17. Amethod for performing non-contact material characterization onsubstrates, comprising the steps of: (a) positioning a wafer carrier inan ancillary chamber of an epitaxial growth apparatus, said wafercarrier holding at least one substrate thereon, said epitaxial growthapparatus having a processing chamber in communication with saidancillary chamber, said processing chamber being adapted to deposit amaterial on the at least one substrate held on said wafer carrier; (b)performing photoluminescence spectroscopy on the material deposited onthe at least one substrate held on the wafer carrier while the wafercarrier is disposed in the ancillary chamber; and (c) adjustingconditions in the epitaxial growth apparatus based on informationobtained during the step of performing photoluminescence spectroscopy,in order to optimize the conditions for a subsequent set of substrates.18. A method as claimed in claim 17 wherein said step of performingphotoluminescence spectroscopy includes directing at least one beam ofradiant energy towards the wafer carrier and moving the beam of radiantenergy across a surface of the wafer carrier.
 19. A method as claimed inclaim 18 wherein the step of moving the beam of radiant energy comprisesmoving a translating mechanism in one dimension.
 20. A method as claimedin claim 18 wherein the wafer carrier has a center and an outer edge,the step of moving the beam of radiant energy comprising moving the beambetween the center and the outer edge.
 21. A method as claimed in claim18 wherein the step of moving the beam of radiant energy comprisesmoving a translating mechanism in two dimensions.
 22. A method asclaimed in claim 18 wherein the step of moving the beam of radiantenergy comprises pivoting the beam of radiant energy.
 23. A method asclaimed in claim 17 wherein said step of performing photoluminescencespectroscopy includes directing at least one beam of radiant energytowards the wafer carrier and rotating the wafer carrier about a centralaxis of the carrier.
 24. A method as claimed in claim 17 wherein saidstep of performing photoluminescence spectroscopy includes directing atleast one beam of radiant energy towards the wafer carrier andmonitoring one or more of the properties of the material deposited onthe at least one substrate that is contacted by the at least one beam ofradiant energy.
 25. A method as claimed in claim 24 further comprisingstoring the monitored properties in a memory device.
 26. A method asclaimed in claim 24 further comprising identifying a geometricalcoordinate of a location on the wafer carrier contacted by the at leastone beam of radiant energy, and further comprising associating themonitored properties with the geometrical coordinate correspondingthereto.
 27. A method as claimed in claim 17 further comprising the stepof performing an epitaxial process on the at least one substrate on thewafer carrier.
 28. A method as claimed in claim 27 further comprisingmoving the wafer carrier into the ancillary chamber of the epitaxialgrowth apparatus after said step of performing an epitaxial process. 29.A method as claimed in claim 28 wherein said step of performingphotoluminescence spectroscopy further includes monitoring one or moreof the properties of the at least one substrate.
 30. A method as claimedin claim 28 wherein the ancillary chamber is a transfer chamberconnecting multiple epitaxial process chambers.
 31. A method as claimedin claim 30 wherein said step of performing photoluminescencespectroscopy further includes monitoring one or more of the propertiesof the at least one substrate.
 32. A method as claimed in claim 31further comprising the step of adjusting conditions in at least one ofthe epitaxial process chambers based on the monitored properties inorder to adjust a process to be applied to the at least one substrateheld on the wafer carrier.
 33. A method as claimed in claim 31 furthercomprising the step of selecting one of the epitaxial process chambersfor additional processing based on the monitored properties in order tooptimize a process to be applied to the at least one substrate held onthe wafer carrier.
 34. A method as claimed in claim 28 wherein theancillary chamber is a load lock.